The requirements of a modern audio playback system have changed, during the years. From single channel (mono) to dual channel (stereo) up to multi-channel systems, like 5.1- and 7.1 Surround or even wave field synthesis, the number of used loudspeaker channels has increased. Even systems with elevated speakers are to be seen in modern cinemas. This aims at giving the listener an audio experience of a recorded or artificially created audio scene, with respect to sense of reality, immersion and envelopment that comes as close to the real audio scene as possible or alternatively best reflects the intentions of the sound engineer (see e.g., M. Morimoto, “The Role of Rear Loudspeakers in Spatial Impression”, in 103rd Convention of the AES, 1997; D. Griesinger, “Spaciousness and Envelopment in Musical Acoustics”, in 101st Convention of the AES, 1996; K. Hamasaki, K. Hiyama, and R. Okumura, “The 22.2 Multichannel Sound System and Its Application”, in 118th Convention of the AES, 2005). However, there are at least two drawbacks: due to the plurality of available sound systems, with respect to the number of used loudspeakers and their recommended positioning, there is no general compatibility between all these systems. Furthermore, any deviation from the recommended loudspeaker positioning will result in a compromised audio scene and, therefore, decreases the spatial audio experience of the listener, and hence, the spatial quality.
In a real world application, multi-channel playback systems are often not configured correctly with respect to loudspeaker positioning. In order not to distort the original spatial image of an audio scene which would result from a faulty positioning, a flexible high quality system is needed which is able to compensate for these setup mismatches. State-of-the-art approaches often lack the ability to describe a complex and maybe artificially-generated sound scene where, for example, more than one direct source per frequency band and time instant appears.